Ultra-broadband Emission Research Articles

Ultra-broadband cyan-to-orange emitting Ba1+xSr1−xGa4O8:Bi3+ phosphors: luminescence control and optical temperature sensing

Controllable cyan-to-orange tuning and optical thermometry in Ba1+xSr1−xGa4O8:Bi3+ phosphors with ultra-broadband emission were realized based on crystal filed control at multiple emission centers.

New lead bromide chiral perovskites with ultra-broadband white-light emission

Herein, we present for the first time on the synthesis and luminescence mechanism of two chiral perovskits with white-light emission and an achiral perovskite featuring a spectral blueshift.

Dual-site occupancy induced broadband cyan emission in Ba2CaB2Si4O14:Ce3+

Dual-site occupancy of Ce3+ on Ba2+ and Ca2+ sites produces ultra-broadband cyan emission, fully covering the blue to green region.

Ultra-broadband near-infrared emission CuInS2/ZnS quantum dots with high power efficiency and stability for the theranostic applications of mini light-emitting diodes.

Broadband near-infrared CuInS2/ZnS quantum dots with up to 94.8% quantum yield were synthesized with fast precursor decomposition leading to monomer conversion improvement. In the mini-LED package, the device showed high power efficiency and stability was also demonstrated with a penetration test and vein imaging showing its potential biomedical application in the theranostics field.

Dual-Band Luminescent Lead-Free Antimony Chloride Halides with Near-Unity Photoluminescence Quantum Efficiency

Low-dimensional organic–inorganic metal halide hybrids (OIMHs) with an ultrabroad-band emission are promising as downconversion phosphors for solid-state lighting. However, toxicity of Pb and low p...

Self‐Trapped Exciton to Dopant Energy Transfer in Rare Earth Doped Lead‐Free Double Perovskite

AbstractLow dimensional halide perovskites with self‐trapped excitons (STEs) emission have emerged as promising white light phosphors because of their ultrabroadband emission covering the entire visible spectrum from 400 to 800 nm. Such a broad emission from a single material can overcome emission color change and self‐absorption problems within multiple phosphors. However, the color rendering index (CRI) and correlated color temperature (CCT) as two essential parameters of white light quality can hardly be modulated in these perovskite materials. Here, rare earth ion Ho3+ is introduced into Cs2(Na,Ag)InCl6 for the first time, utilizing the hydrothermal method. Besides the strong warm white STEs emission, the as‐synthesized materials exhibit effective characteristic emission of Ho3+ in the visible region. Further, the mechanism of associated emission is explored and the existence of energy transfer from STEs to rare earth is first confirmed. A white light‐emitting diode (LED) prototype is also fabricated by employing the Ho3+ doped Cs2(Na,Ag)InCl6 as the color conversion material on a commercial 365 nm GaN LED chip, achieving an improved CRI from 70.3 to 75.4 compared to the pure Cs2(Na,Ag)InCl6. This result suggests a promising way to achieve high quality single phase all‐inorganic white phosphors and this mechanism has enormous potentials in other optoelectronic applications.

Crystal-field engineering of ultrabroadband mid-infrared emission in Co2+-doped nano-chalcogenide glass composites

Tunable and ultrabroadband mid-infrared (MIR) emissions in the range of 2.5–4.5 μm are firstly reported from Co2+-doped nano-chalcogenide (ChG) glass composites. The composites embedded with a variety of binary (ZnS, CdS, ZnSe) and ternary (ZnCdS, ZnSSe) ChG nanocrystals (NCs) can be readily obtained by a simple one-step thermal annealing method. They are highly transparent in the near- and mid-infrared wavelength region. Low-cost and commercially available Er3+-doped fiber lasers can be used as the excitation source. By crystal-field engineering of the embedded NCs through cation- or anion-substitution, the emission properties of Co2+ including its emission peak wavelength and bandwidth can be tailored in a broad spectral range. The phenomena can be accounted for by crystal-field theory. Such nano-ChG composites, perfectly filling the 3–4 μm spectral gap between the oscillations of Cr2+ and Fe2+ doped IIVI ChG crystals, may find important MIR photonic applications (e.g., gas sensing), or can be used directly as an efficient pump source for Fe2+: IIVI crystals which are suffering from lack of pump sources.

Ultra-broadband 1.0 μm band emission spectroscopy in Pr3+/Nd3+/Yb3+ tri-doped tellurite glass.

Tellurite glasses doped with trivalent Pr3+, Nd3+ and Yb3+ ions were prepared using conventional high-temperature melt-quenching technique and their optical absorption, near-infrared emission, X-ray diffraction (XRD), Raman spectrum, and differential scanning calorimeter (DSC) curve were measured. Upon excitation at 488 nm, an ultra-broadband near-infrared emission extending from 800 to 1120 nm was found to appear owing to the overlapping of the emission bands centered at 900 and 1035 nm of Pr3+, 880 and 1060 nm of Nd3+ as well as 978 nm of Yb3+, respectively. The energy transfer mechanism among Pr3+, Nd3+ and Yb3+ ions which was responsible for the observed ultra-broadband near-infrared emission was investigated to understand the luminescent phenomena. In addition, Judd-Ofelt theory was applied to predict the radiative properties of doped rare-earth ions, and some important radiative parameters such as radiative transition probability, branching ratio and radiative lifetime were derived. Meanwhile, the structural information of amorphous nature and vibrational units was revealed by the XRD pattern and Raman spectrum. Also, the DSC curve displayed the good thermal stability to resist thermal damage for studied tellurite glass with high glass transition temperature. The results indicate that Pr3+/Nd3+/Yb3+ tri-doped tellurite glass is a promising material for ultra-broadband fiber lasers operating around 1.0 μm near-infrared band.

Enhancing 1.8 μm emission from ultra-broadband Tm-Bi-Er tri-doped fluorotellurite glasses for fiber amplifiers and near-infrared lasers

Abstract Fluorotellurite glasses tri-doped with Tm 3+ , Er 3+ and Bi ions were investigated. The measured parameter ΔT (116 °C) confirmed that the prepared glasses had good stability. An ultra-broadband fluorescence emission (950–1670 nm) was observed with a full-width at half-maximum (FWHM) of 560 nm, which covered the entire bands of O, E, S, C, L and U. The 1800 nm fluorescence intensity of Tm 3+ /Er 3+ co-doped and Tm 3+ /Er 3+ /Bi tri-doped glasses was enhanced compared to Tm 3+ doped glass, which indicates that there is energy transfer between Tm 3+ , Er 3+ and Bi ions. The maximum fluorescence lifetime of the prepared glasses was 7.39 ms, indicating the excellent fluorescence performance at 1800 nm. Additionally, the maximum absorption cross section (σ abs = 1.77 × 10 −20 cm −2 ) and emission cross section (σ em = 7.61 × 10 −20 cm −2 ) suggest that the Tm 3+ /Er 3+ /Bi tri-doped glasses have good optical absorption properties and high gain fluorescence emission. The above results indicate that the Tm 3+ /Er 3+ /Bi tri-doped fluorotellurite glasses have good application prospects in the field of fiber amplifiers and near-infrared lasers.

Ultra-broadband mid-infrared emission from a Pr3+/Dy3+ co-doped selenide-chalcogenide glass fiber spectrally shaped by varying the pumping arrangement [Invited

In this contribution, a comprehensive experimental study of photoluminescence from Pr3+/Dy3+ co-doped selenide-chalcogenide multimode fiber samples is discussed. The selenide-chalcogenide multimode fiber samples co-doped with 500 ppm of Pr3+ ions and 500 ppm of Dy3+ ions are prepared using conventional melt-quenching. The main objective of the study is the analysis of the pumping wavelength selection on the shape of the output spectrum. For this purpose, the Pr3+/Dy3+ co-doped selenide-chalcogenide multimode fiber samples are illuminated at one end using pump lasers operating at the wavelengths of 1.32 µm, 1.511 µm and 1.7 µm. The results obtained show that the Pr3+/Dy3+ ion co-doped selenide-chalcogenide multimode fiber emits photoluminescence spanning from 2 µm to 6 µm. Also it is demonstrated that, by varying the output power and wavelength of the pump sources, the spectral shape of the emitted luminescence can be modified to either reduce or enhance the contribution of radiation within a particular wavelength band. The presented results confirm that Pr3+/Dy3+ co-doped selenide-chalcogenide multimode fiber is a good candidate for the realization of broadband spontaneous emission fiber sources with shaped output spectrum for the mid-infrared wavelength region.

Er3+/Pr3+/Nd3+ tri-doped tellurite glass for ultra-broadband amplification applications

The near-infrared band luminescence from Er3+/Pr3+/Nd3+ tri-doped tellurite glasses were investigated in this work. The tellurite glasses were prepared by melt-quenching method and under the excitation of 488 nm laser, an ultra-broadband emission from 1260 to 1650 nm with FWHM about 256 nm was found to appear owing to the perfect overlapping of emission bands from Er3+, Pr3+ and Nd3+, respectively. Additionally, the studied tellurite glasses possess high glass transition temperature with Tg > 420 °C. The ultra-broadband and flat emission properties as well as good thermal stability indicates that Er3+/Pr3+/Nd3+ tri-doped tellurite glass has great application prospect in near-infrared band broadband fiber amplifiers.

In situ instant generation of an ultrabroadband near-infrared emission center in bismuth-doped borosilicate glasses via a femtosecond laser

Bismuth (Bi)-doped photonic materials, which exhibit broadband near-infrared (NIR) luminescence (1000–1600 nm), are evolving into interesting gain media. However, the traditional methods have shown their limitations in enhancing Bi NIR emission, especially in the microregion. Consequently, the typical NIR emission has seldom been achieved in Bi-doped waveguides, which highly restricts the application of Bi-activated materials. Here, superbroadband Bi NIR emission is induced in situ instantly in the grating region by a femtosecond (fs) laser inside borosilicate glasses. A series of structural and spectroscopic characterizations are summoned to probe the generation mechanism. And we show how this novel NIR emission in the grating region can be enhanced significantly and erased reversibly. Furthermore, we successfully demonstrate Bi-activated optical waveguides. These results present new insights into Bi-doped materials and push the development of broadband waveguide amplification.

Air-Stable, Lead-Free Zero-Dimensional Mixed Bismuth-Antimony Perovskite Single Crystals with Ultra-broadband Emission.

Lead-free zero-dimensional (0D) organic-inorganic metal halide perovskites have recently attracted increasing attention for their excellent photoluminescence properties and chemical stability. Here, we report the synthesis and characterization of an air-stable 0D mixed metal halide perovskite (C8 NH12 )4 Bi0.57 Sb0.43 Br7 ⋅H2 O, in which individual [BiBr6 ]3- and [SbBr6 ]3- octahedral units are completely isolated and surrounded by the large organic cation C8 H12 N+ . Upon photoexcitation, the bulk crystals exhibit ultra-broadband emission ranging from 400 to 850 nm, which originates from both free excitons and self-trapped excitons. This is the first example of 0D perovskites with broadband emission spanning the entire visible spectrum. In addition, (C8 NH12 )4 Bi0.57 Sb0.43 Br7 ⋅H2 O exhibits excellent humidity and light stability. These findings present a new direction towards the design of environmentally-friendly, high-performance 0D perovskite light emitters.

Terahertz imaging with room-temperature terahertz difference-frequency quantum-cascade laser sources.

We demonstrate high-quality non-destructive imaging using a broadband terahertz quantum cascade laser source based on Cerenkov difference-frequency generation. The source exhibited ultra-broadband terahertz emission spectra, as well as a single-lobed Gaussian-like far-field pattern at -30 °C. These features allowed us to build a compact imaging system with a high spatial resolution, from which a nearly theoretical minimum beam spot size was obtained. As a result, we achieve well-resolved, high-contrast images of objects obscured by opaque materials. We also achieved terahertz imaging with the THz DFG-QCL operated at room temperature.

Ultrabroad-band, red sufficient, solid white emission from carbon quantum dot aggregation for single component warm white light emitting diodes with a 91 high color rendering index.

An ultrabroad-band solid white emission from carbon quantum dot aggregation with a full width at half maximum over 200 nm throughout the entire visible light window and, even better, with a sufficient red component is first reported. UV pumped WLEDs are fabricated by integrating phosphors onto a UV-LED chip, and they show favorable warm white light characteristics with CIE coordinates of (0.42, 0.38) and a 91 high color rendering index.

Praseodymium ion doped K+-Na+ thermal ion-exchangeable waveguide-adaptive aluminum germanate glasses.

Intense multi-peak red fluorescence and effective near-infrared (NIR) ultra-broadband emission have been observed in Pr3+ doped ion-exchangeable aluminum germanate (NMAG) glasses. The maximum emission cross section for P03→F23 red emission is up to 100.58×10-21 cm2, and the NIR emission corresponding to D21→G41 transition possesses a full-width at half-maximum (FWHM) of 210nm. Although the obvious cross-relaxation (CR) process at high concentration causes a decrease of the quantum efficiency, the CR broadens the spectral FWHM effectively from another perspective. The admirable red fluorescence trace and the NIR single-mode transmission confirm that Pr3+ doped NMAG glass planar waveguides can support the generation of visible fluorescence and the amplification of infrared signal. For a waveguide channel ion-exchanged in molten KNO3 for 2h, the single-mode field diameters at 1.55μm are identified to be 10.4μm in the horizontal direction and 6.5μm in the vertical direction, implying an acceptable overlap with a standard single-mode fiber. Effective red fluorescence and broad NIR emission demonstrate that Pr3+ doped NMAG glasses are a promising substrate in developing irradiative luminescence sources and ultra-broadband waveguide amplifiers, especially operating at the entire S-, C-, and L- bands.

Recent progress in terahertz difference-frequency quantum cascade laser sources

Abstract Terahertz quantum cascade laser (QCL) sources based on intra-cavity difference frequency generation are currently the only electrically pumped monolithic semiconductor light sources operating at room temperature in the 1–6-THz spectral range. Relying on the active regions with the giant second-order nonlinear susceptibility and the Cherenkov phase-matching scheme, these devices demonstrated drastic improvements in performance in the past several years and can now produce narrow-linewidth single-mode terahertz emission that is tunable from 1 to 6 THz with power output sufficient for imaging and spectroscopic applications. This paper reviews the progress of this technology. Recent efforts in wave function engineering using a new active region design based on a dual-upper-state concept led to a significant enhancement of the optical nonlinearity of the active region for efficient terahertz generation. The transfer of Cherenkov devices from their native semi-insulating InP substrates to high-resistivity silicon substrates resulted in a dramatic improvement in the outcoupling efficiency of terahertz radiation. Cherenkov terahertz QCL sources based on the dual-upper-state design have also been shown to exhibit ultra-broadband comb-like terahertz emission spectra with more than one octave of terahertz frequency span. The broadband terahertz QCL sources operating in continuous-wave mode produces the narrow inter-mode beat-note linewidth of 287 Hz, which indicates frequency comb operation of mid-infrared pumps and thus supports potential terahertz comb operation. Finally, we report the high-quality terahertz imaging obtained by a THz imaging system using terahertz QCL sources based on intra-cavity difference frequency generation.

Pr3+/Er3+ co-doped tellurite glass with ultra-broadband near-infrared fluorescence emission

Pr3+/Er3+ co-doped tellurite glass with composition 80TeO2-10Na2O-5WO3-5Nb2O5 was synthesized by the conventional melt-quenching technique, and the obtained glass was characterized by the UV/Vis/NIR absorption spectrum, near-infrared fluorescence spectrum, differential scanning calorimeter (DSC) curve, X-Ray diffraction (XRD) pattern and Raman spectrum. Under the 488nm excitation, it was found that Pr3+/Er3+ co-doped tellurite glass could emit an ultra-broadband near-infrared fluorescence which extended from 1200 to 1650nm with full-width at half-maximum (FWHM) of about 236nm, and this ultra-broadband fluorescence was contributed by the multichannel emissions of Pr3+ and 1.53µm band emission of Er3+. The luminescent mechanism and energy transfer processes between Pr3+ and Er3+ ions which are responsible for the observed ultra-broadband fluorescence were analyzed. Meanwhile, optical absorption bands that are assigned with corresponding electronic transitions with respect to Pr3+ and Er3+ ions were identified from the measured absorption spectrum, and based on the optical absorption data, the gain coefficient and important spectroscopic parameters like Judd-Ofelt intensity parameter, spontaneous radiative transition probability, radiative lifetime and branching ratio were calculated to elucidate the radiative properties of doped rare-earth ions. In addition, the DSC curve exhibited the good thermal stability of glass host with ΔT >150°C, Raman spectral study displayed the presence of different vibrational groups and XRD pattern confirmed the amorphous structural nature of the prepared glass. The present results indicate that Pr3+/Er3+ co-doped tellurite glass is promising for the ultra-broadband near-infrared band fiber amplifiers covering the expanded low-loss communication window.

Solid Solution Quantum Dots with Tunable Dual or Ultrabroadband Emission for LEDs.

Quantum dots that efficiently emit white light directly or feature a "candle-like" orange photoluminescence with a high Stokes shift are presented. The key to obtaining these unique emission properties is through controlled annealing of the core Cu-In-Ga-S quantum dots in the presence of zinc ions, thus forming Zn-Cu-In-Ga-S solid solutions with different distributions of the substitution and dopant elements. The as-obtained nanocrystals feature excellent quantum yields of up to 82% with limited or even eliminated reabsorption and a color rendering index of bare particles of up to 88, enabling the production of high-quality white LEDs using a single color converter layer. Furthermore, the color properties can be tuned by changing the experimental conditions as well as by varying the excitation wavelength. The multicomponent luminescence mechanism is discussed in detail based on similar literature reports. White LEDs with unparalleled color quality and competitive luminous efficacies are presented herein.

Record power, ultra-broadband supercontinuum source based on highly GeO2 doped silica fiber.

We demonstrate highly germania doped fibers for mid-infrared supercontinuum generation. Experiments ensure a highest output power of 1.44 W for a broadest spectrum from 700 nm to 3200 nm and 6.4 W for 800 nm to 2700 nm from these fibers, while being pumped by a broadband Erbium-Ytterbium doped fiber based master oscillator power amplifier. The effect of repetition frequency of pump source and length of germania-doped fiber has also been investigated. Further, germania doped fiber has been pumped by conventional supercontinuum source based on silica photonic crystal fiber supercontinuum source. At low power, a considerable broadening of 200-300 nm was observed. Further broadening of spectrum was limited due to limited power of pump source. Our investigations reveal the unexploited potential of germania doped fiber for mid-infrared supercontinuum generation. These measurements ensure the potential of germania based photonic crystal fiber or a step-index fiber supercontinuum source for high power ultra-broad band emission being by pumped a 1060 nm or a 1550 nm laser source. To the best of our knowledge, this is the record power, ultra-broadband, and all-fiberized supercontinuum light source based on silica and germania fiber ever demonstrated to the date.